The present invention relates to a color adjustment method, an color adjustment method implementation program and a program storage medium for generating a gradation correction curve representing the relationship of cyan C, magenta M, yellow Y and black K between two image output apparatuses, a printing machine and a color proof printer, based on the colorimetry of a color chart, and for reproducing the colors of the printed matter outputted from a printer by a color proof printer using the aforementioned gradation correction curve.
In a prior art dot type color proof printer, the colors of C, M, Y and K coloring materials are close to ink colors of printing machine, so correction (gain dot curve correction) of the difference in the dot size for each of C, M, Y and K is carried out based on the result of measuring the dot percentage, whereby colors can be matched to a printing machine to a certain extent.
Further, the gradation correction curve of each color is generated based on the output of each single color, and colors can be matched to the printing machine to a certain extent using the aforementioned gradation correction curve, according to the prior art.
However, although reproducibility of each color can be ensured by the gradation correction curve generated by the output of each of colors C, M, Y and K, the gray color produced by overlaying of three colors, C, M and Y may not be satisfactory in some cases. It looks reddish or greenish, and the color tones of the entire image are not matched correctly, according to the prior art.
The present invention is intended to solve the aforementioned problems. The object is to provide a color adjustment method for matching the gray composed of a combination of C, M and Y, and color tones of the entire image when the output of a color proof printer is matched to the output of a printing machine.
The present invention uses the following means to solve the aforementioned problems:
A first color adjustment method (1) is characterized in that,
in a first color image output apparatus as a target of color matching and a second color image output apparatus for reproducing that color,
a gradation correction curve is generated for each color in such a way that the values for four colors, cyan C, magenta M, yellow Y and black K or three color, C, M and Y to be input into the aforementioned first color image output apparatus are input values for the gradation correction curve, while the values for four colors, C, M, Y and K or three color, C, M and Y to be input into the aforementioned second color image output apparatus are output values for the gradation correction curve; and
conversion of C, M, Y and K is performed for image data by the aforementioned gradation correction curve so that the output matched to the color of the first color image output apparatus can be obtained by the aforementioned second color image output apparatus;
said color adjusting method further characterized in that the aforementioned gradation correction curve is generated based on the first color chart outputted from the aforementioned first color image output apparatus and the second color chart outputted from the aforementioned second color image output apparatus.
A second color adjustment method (2) is characterized in that said first color chart and second color chart contain the colors outputted by overprinting of fundamental colors.
A third color adjustment method (3) is characterized in that said first color chart contains at least one or two gray colors outputted by overprinting of three fundamental colors, C, M and Y, in equal amounts.
A fourth color adjustment method (4) is a program for implementing on a computer the color adjustment method according any one of the aforementioned first to third color adjustment methods.
A fifth color adjustment method (5) is characterized by comprising a computer readable memory medium for storing the program according to the aforementioned fourth method.